1. Field of Invention
The present invention relates to plasma processing and more particularly to a method for determining a seasoning state of a plasma processing system.
2. Description of Related Art
The fabrication of integrated circuits (IC) in the semiconductor industry typically employs plasma to create and assist surface chemistry within a plasma reactor necessary to remove material from and deposit material to a substrate. In general, plasma is formed within the plasma reactor under vacuum conditions by heating electrons to energies sufficient to sustain ionizing collisions with a supplied process gas. Moreover, the heated electrons can have energy sufficient to sustain dissociative collisions, and therefore, a specific set of gases under predetermined conditions (e.g., chamber pressure, gas flow rate, etc.) are chosen to produce a population of charged species and chemically reactive species suitable to the particular process being performed within the chamber (e.g., etching processes where materials are removed from the substrate or deposition processes where materials are added to the substrate).
Typically, during plasma processing such as for example during etch applications, it is necessary to xe2x80x9cseasonxe2x80x9d the plasma processing system following a period of process system maintenance, i.e. chamber cleaning, process kit replacement, etc. Prior to initiating production, several substrates, typically of order a hundred wafers, are processed through the plasma processing system in order to form a xe2x80x9cseasoningxe2x80x9d film on the chamber interior and, thus, facilitate repeatable process performance for the substrates to follow. In general, the number of substrates executed is chosen arbitrarily high to assure proper xe2x80x9cseasoningxe2x80x9d; however, common practice can lead to excessive cost and time consumption.
The present invention provides for a plasma processing system that comprises a process chamber, a plasma source and a detection system, wherein the detection system comprises a light detection device and a controller. The controller is useful for determining a seasoning state of the plasma processing system.
The present invention further provides a method of determining the seasoning state of a plasma processing system comprising the steps of forming a first plasma in the process chamber utilizing the plasma source; measuring a first signal related to light emitted from the first plasma using the light detection device and storing the first signal; forming a second plasma in the process chamber utilizing the plasma source; measuring a second signal related to light emitted from the second plasma using the light detection device and storing the second signal; and correlating a change between the first signal and the second signal with a seasoning state of the plasma processing system.
It is an object of the present invention that forming the first plasma corresponds to a first substrate, and forming the second plasma corresponds to a second substrate.
It is another object of the present invention that forming the first plasma corresponds to a first time during the processing of a substrate, and forming the second plasma corresponds to a second time during the processing of the substrate.
It is another object of the present invention that the first plasma is the same as the second plasma.
The present invention further provides an alternate method of determining a seasoning state of a plasma processing system comprising the steps of loading a substrate into the plasma processing system; forming a plasma to facilitate processing of the substrate; measuring a signal related to light emitted from the plasma; comparing the signal with a target signal determined for the plasma processing system; and determining a seasoning state of the plasma processing system from the comparison of the signal with the target signal.
The present invention further provides an alternate method of determining a seasoning state of a plasma processing system comprising the steps of loading a first substrate into the plasma processing system; forming a plasma to facilitate processing of the first substrate; measuring a first signal related to light emitted from the plasma and storing the first signal using the controller; unloading the first substrate; loading a second substrate into the plasma processing system; forming a plasma to facilitate processing of the second substrate; measuring a second signal related to light emitted from the plasma and storing the second signal using the controller; determining a difference signal from the second signal and the first signal; comparing the difference signal with a target signal; and determining a seasoning state of the plasma processing system from the comparing of the difference signal with the target signal.